Timur I. Burganov

Application of time-dependent density functional theory and optical spectroscopy toward the rational design of novel 3,4,5-triaryl-1-R-1,2-diphospholes.

Twenty 3,4,5-triaryl-1-R-1,2-diphospholes were studied within the framework of density functional theory (DFT) and experimentally by UV/vis spectroscopy to check their suitability for opto-electronic applications. Time-dependent DFT (TD-DFT) calculations employing the PBE0 hybrid density functional combined with moderately sized def-TZVP basis set were shown to excellently reproduce the experimental absorption spectra of various 1,2-diphospholes. Frontier molecular orbital analysis reveals that HOMO and LUMO are mainly localized on the diphosphole ring and, to some extent, on the aryl moieties. The HOMO-LUMO energy gap can be easily tuned by variation of substituents introduced in para-positions of the aryl moieties and, to a lesser extent, by modification of the R group at phosphorus atom. As a result, both position and intensity of the absorption bands with highest wavelength are strongly influenced by the above structural changes. The UV-spectra simulations reveal that the introduction of donor groups like para-OMe, para-NMe2, and para-N(H)Ph, which are in n-π conjugation with the aryl moieties, should result in absorption of visible light by the corresponding 1,2-diphospholes, thus making them promising candidates for new functional materials.

Comparative Study of Conjugational Effects in 3,4,5-Triaryl-1-R-1,2-Diphospholes and 3,4,5-Triaryl-1,2-Diphosphacyclopentadienide-Anions

GRAPHICAL ABSTRACT Abstract The strength of conjugation between the phosphorus ring of 3,4,5-triaryl-1,2-diphosphacyclopentadienide-anion and exocyclic phenyl groups has been quantitatively characterized by the use of Raman activities of the bands of the phenyl substituents and the structural parameters obtained by an X-ray diffraction study. It is shown that conjugation in 1,2-diphospholides is very similar to conjugation of phenyl groups with the diene system of 1-R-1,2-diphospholes. The conjugation produces a dramatic intensification of Raman bands and a simultaneous bathochromic shift of the whole electronic absorption spectra for both types of phosphorus heterocycles.

The influence of different substituents on the geometrical changes in the heterocyclic moiety of 1,2-diphospholes

GRAPHICAL ABSTRACT ABSTRACT It is shown that increase of steric bulk of R group of 1R-1,2-diphospholes results in decrease of the pyramidality of P(III) atom, but has little impact on a planarity of the entire heterocycle in the case of R = Alk. At the same time, planarization of the heterocycle reported elsewhere for R = SnMe3 or SiMe3 is accompanied by moderate increase of the P(III) pyramidality relative to the case of R = Alk. This difference could be related to effects of π-σ conjugation between P-Sn/P-Si moiety and the dienic system of the 1,2-diphosphole.

Conjugation effects and optical spectra of 1,2-diphosphole cycloadducts

Quantum chemical calculations and a comparative analysis of Raman spectra of 3,4,5-triphenyl-1-propyl-1,2-diphosphole (1), anti-endo-4,7,8,9-tetraphenyl-10-propyl-4-aza-1,10-diphosphatricyclo[5.2.1.02,6]deca-8-ene-3,5-dione (2) and 1,2,6,7-tetraphospha-3,4,5,8,9,10-hexaphenyltricyclo[5.3.0.02,6]deca-3,9-diene (3) made it possible to explain considerable differences in the UV absorption spectra of these compounds. The phenyl groups in the compounds under study, despite the steric factor, are conjugated with the π-system of the heterocycle, which in the case of diphosphole 1 comprises π-electrons of the C=C and P=C bonds. The disturbance of this diene system in molecules 2 and 3 decreases the effective length of conjugation of phenyl groups with the attached double bonds of the phosphorus-containing ring, that results in the hypsochromic shift of the π—π* electron transition bands in the UV absorption spectrum from 411 to 312 nm. The formation in molecule 3 of the four-membered ring P4, which is a new chromophore group, leads to the appearance of an additional absorption band with the maximum at ∼342 nm.

Novel amphiphilic conjugates of p-tert-butylthiacalix[4]arene with 10,12-pentacosadiynoic acid in 1,3-alternate stereoisomeric form. Synthesis and chromatic properties in the presence of metal ions

For the first time amphiphilic receptors based on the 1,3-alternate stereoisomeric form of thiacalix[4]arene, bearing carboxyl/sulphonate polar headgroups on one side and 10,12-pentacosadiynoic acid (PCDA) residues on another side of the macrocyclic plane, were synthesized. It was shown that embedding of synthesized macrocycles in PCDA vesicles results in stable colloids with a size around 300 nm. The temperature of ultrasonication before UV irradiation has a critical impact on the packing of vesicles for better polymerization. The increase of calixarene content in PCDA vesicles causes a decrease in the degree of PCDA polymerization. Nevertheless, calixarene additives dramatically change the colorimetric response of photopolymerized PCDA vesicles toward metal ions. Vesicles with 10 mol% content of calixarene have significant colorimetric response toward lanthanide ions with a detection limit up to 8 μM. The colorimetric response in the series of lanthanide ions depends on the ionic radius, and the greatest response was found for the largest La(III) ion. It was found that binding of calixarene–PCDA vesicles with lanthanide ions results in the formation of large 1 μm aggregates followed by sedimentation. Thus, the mechanism of colorimetric response of calixarene-decorated polydiacetylene vesicles toward lanthanide ions includes the distortion of the calixarene cavity provoking perturbation of the PDA backbone accompanied by metal-induced aggregation of functionalized vesicles with sedimentation of particles. Therefore, calixarene–PCDA vesicles have great potential for the future design of bifunctional colloids with sensor and separation applications.

A fresh look at participation of phosphorus atom in conjugation

GRAPHICAL ABSTRACT ABSTRACT The strength of conjugation between the lone pair on phosphorus atom and aryl, alkenyl and styryl moieties of several phosphines has been quantitatively characterized by the use of Raman intensities of the bands of the above-mentioned substituents. It is shown that conjugation in the phosphines produces an intensification of Raman bands and a simultaneous bathochromic shift of the electronic absorption spectra for all the phosphines, except of phenylphosphine PhPH2, where the lone pair on PIII does not conjugate with phenyl moiety. Nevertheless, the lone pair is able to conjugation within more expanded aromatic π-systems, and the conjugational effects are strongly enhanced as π-system of arylphosphines expands.